US20230184918A1

US20230184918A1 - Radar Detection Sensor, System, and Method

Info

Publication number: US20230184918A1
Application number: US17/998,532
Authority: US
Inventors: Federico Corradi; Emmanouil Sifalakis
Original assignee: Stichting Imec Nederland
Current assignee: Stichting Imec Nederland
Priority date: 2020-05-13
Filing date: 2021-03-04
Publication date: 2023-06-15
Also published as: WO2021228450A1; EP3910369A1

Abstract

A detection sensor includes a signal transmitter configured to successively generate and transmit a detection signal in a plurality of observation intervals and a signal receiver configured to receive a scatter signal. The scatter signal includes a plurality of frequency bins resulting from a scattering of the detection signal in the plurality of observation intervals. Moreover, the detection sensor includes an event generator configured to compare a present scatter signal to a previous scatter signal, separately for each of the plurality of frequency bins, and generate an event for each frequency bin, in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national phase application of international application no. PCT/EP2021/055428 filed on Mar. 4, 2021, which claims priority to European patent application no. 20174295.4 filed on May 13, 2020, the contents of both being incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present invention relates to a detection sensor, a detection system, and a detection method using active sensing, especially using radar signals.

BACKGROUND

In active sensing, especially in active radar sensing, a detection signal is transmitted towards an object, scattered, and received as a scatter signal. From the received scatter signal, information regarding the object which scattered the detection signal can be derived. Since in typical applications, frequency sweeps, also called chirps, are transmitted within the detection signal repeatedly, the received scatter signal comprises a great amount of data. Recording, storing, transferring, and processing this data poses great challenges.
For example, the document US 2018/0329049 A1 shows a radar-based active sensing system, where the problem of a large data volume is tackled by increasing the time interval between transmitting chirps within the detection signal. This significantly increases the time interval between receiving scattered chirps within the scattered signal and thereby significantly reduces the amount of data to process. This approach though is also disadvantageous, since important information might be missed between the chirps.

SUMMARY

An object of the present invention therefore is to provide a detection sensor, detection system and method, which allow for reducing the system complexity while at the same time not losing valuable data.
A detection sensor comprises a signal transmitter, configured to successively generate and transmit a detection signal, in a plurality of observation intervals, and a signal receiver, configured to receive a scatter signal, comprising a plurality of frequency bins, resulting from a scattering of the detection signal, in the plurality of observation intervals. Moreover, the detection sensor comprises an event generator, configured to compare a present scatter signal to a previous scatter signal, separately for each of the plurality of frequency bins, and generate an event for each frequency bin, in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount. This allows for significantly reducing the amount of data to record, store, transfer and process.
The event generator can be configured to compare the present scatter signal to at least two consecutive previous scatter signals, and to generate an event for each frequency bin, in which the present scatter signal differs from the at least two consecutive previous scatter signals by at least the event threshold amount. This significantly reduces the susceptibility to noise.
In some examples, the event threshold amount is different for at least two frequency bins. Additionally or alternatively, the event threshold amount is preset or user adjustable or automatically dynamically adjustable. Additionally or alternatively, the detection sensor comprises an event threshold determiner, configured to determine the event threshold amount based upon an occurrence of past events, and/or a type of detection object, and/or a detection situation, and/or a noise level. This allows a high flexibility regarding the use of the detection sensor.
In some examples, the present scatter signal is the scatter signal of a present observation interval. The previous scatter signal then is the scatter signal of the observation interval directly previous to the present observation interval. This allows for efficiently processing the signals.
In some examples, the event generator is configured to compare the present scatter signal to the previous scatter signal, with regard to absolute signal values in the time domain and/or to compare the present scatter signal to the previous scatter signal with regard to phase differences with regard to the detection signal. This allows for a significant increase in accuracy.
In some examples, the detection sensor moreover comprises an event transmission interface, connectable to an external event processor. The event generator is configured to transmit the events determined by the event generator through the event transmission interface. This allows for a separate location of the detection sensor and the external event processor, significantly reducing the space necessary for mounting the detection sensor.
In some examples, the signal receiver comprises a single antenna configured to receive the scatter signal, or the signal receiver comprises at least two antennas configured to receive the scatter signal. Additionally, the signal transmitter comprises a single antenna configured to transmit the detection signal, or the signal transmitter comprises at least two antennas configured to transmit the detection signal. This allows for either a simple system construction using a low antenna number or a high detection accuracy, when using a high antenna number.
A detection system comprises a previously described detection sensor and an event processor. This allows for a complete detection within the system.
In some examples, the detection sensor is arranged in a first housing, while the event processor is arranged in a second housing. This allows for a separate location and therefore for a significant reduction in mounting space of the sensor. For example, the detection system could be mounted within a vehicle. The first housing, comprising the detection sensor, might be mounted in the front bumper, while the event processor comprised by the second housing might be mounted beneath the dashboard.
In some examples, the first housing and the second housing are connected through a cable connection or a wireless connection. The cable connection therein can be an electrical cable or a fiber optic cable. In some examples, this connection is a digital connection. This allows for an especially efficient transmission of the events.
In some examples, the first housing does not comprise any further event processing hardware. This further reduces the required mounting space for the first housing.
In some examples, the event processor comprises an event post-processor configured to perform post-processing on the events provided by the event generator. The post-processing comprises a statistical evaluation in the time domain and/or the frequency domain. Additionally or alternatively, the post-processing comprises a one-dimensional filtering regarding the frequency bins, and/or a one-dimensional filtering regarding the observation intervals, and/or a two-dimensional filtering regarding the frequency bins and regarding the observation intervals, and/or a plausibility check. This further increases the accuracy of the detection.
In some examples, the event processor comprises a motion analyzer, configured to perform a motion analysis on the events provided by the event generator, or data generated therefrom. This allows for a complete situation analysis.
In some examples, the event processor comprises an event interpreter, configured to interpret the events provided by the event generator, or data generated therefrom. This allows for a high-level analysis of the situation.
In some examples, the event interpreter is configured to determine a type of detected object and/or a type of movement by a detected object and/or a presence of a person and/or a specific person and/or a type of gesture performed by a person and/or a type of activity performed by a person and/or a type of motion in the spatial domain and/or in the time domain. This allows for a very flexible interpretation.
A method for performing a detection comprises successively generating and transmitting a detection signal, in a plurality of observation intervals, receiving a scatter signal, comprising a plurality of frequency bins, resulting from a scattering of the detection signal, in the plurality of observation intervals, comparing a present scatter signal to a previous scatter signal, separately for each of the plurality of frequency bins, and generating an event for each frequency bin, in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount. This allows for a significant reduction in system complexity.

BRIEF DESCRIPTION OF THE FIGURES

Exemplary embodiments of the invention are now further explained by way of example only with regard to the drawings, in which

FIG. 1 shows a detection sensor, according to an example;

FIG. 2 shows a detection sensor, according to an example;

FIG. 3 shows signals related to the detection sensor, according to an example;

FIG. 4 shows signals and events related to the detection sensor, according to an example; and

FIG. 5 is a block diagram of a method, according to an example.

DETAILED DESCRIPTION

First, we demonstrate the general construction and function of an embodiment of the detection sensor of FIG. 1 . With regard to FIG. 2 , further construction details and function details are described with regard to the embodiment. With regard to FIG. 3 and FIG. 4 , details of the function are described with regard to a number of different signals. Finally, with regard to FIG. 5 , the function of an embodiment of a method is described in detail. Similar entities and reference numbers in different figures have been partially omitted.
In FIG. 1 , a detection system 2 comprising a detection sensor 1 and an event processor 20 is shown. The detection sensor 1 is arranged in a first housing 14, while the event processor 20 is arranged in a second housing 21. The detection sensor 1 comprises a signal transmitter 10, which is configured to generate and transmit a detection signal 4 towards an object 3 to be detected. The detection sensor 1 moreover comprises a signal receiver 11, configured to receive a scatter signal 5, which corresponds to the detection signal 4, scattered by the object 3.
The signal transmitter 10 can comprise one or more transmission antennas for transmitting the detection signal 4. The signal receiver 11 also can comprise one or more reception antennas for receiving the scatter signal 5. The detection sensor 1 moreover comprises an event generator 12, which is connected to the signal receiver 11. Optionally, the event generator 12 is additionally connected to the signal transmitter 10.
Moreover, the detection sensor 1 comprises an event interface 13, which is connectable to an external event processor. In the embodiment shown here, the event interface 13 is connected to the event processor 20 through a connection 15, which is depicted here as a cable connection, for example an electrical cable or a fiber optic cable. Alternatively, the connection 15 can also be a wireless connection. Although not depicted here, a controller for controlling the function of the signal transmitter 10, signal receiver 11, event generator 12, and event interface 13 might additionally be included as part of the detection sensor 1.
In operation, the signal transmitter 10 successively generates and transmits the detection signal 4 in a plurality of observation intervals. The scatter signal 5 is received by the signal receiver 11 in the plurality of observation intervals. The detection signal 4 therein comprises energy components in a plurality of frequency bins. The scatter signal 5 therefore also comprises energy components in a plurality of frequency bins. The signal receiver 11 is configured to receive the scatter signal 5 in a manner that allows a later differentiation of the energy components in the different frequency bins.
The received scatter signal 5 is then handed on to the event generator 12, which compares a present scatter signal 5 to a previous scatter signal 5, separately for each of the plurality of frequency bins. This comparison can be performed on absolute signal values or on phase values with regard to the detection signal 4. For this purpose, the optional connection to the signal transmitter 10 provides information regarding the detection signal 4 or directly the detection signal 4, to the event generator 12.
The event generator 12 then generates an event for each frequency bin, in which the present scatter signal 5 differs from the previous scatter signal 5 by at least an event threshold amount. Instead of only comparing the present scatter signal 5 to the directly previous scatter signal 5, also a comparison of the present scatter signal 5 to a number of previous scatter signals 5 is possible. In this case, an event is generated for each frequency bin, in which the present scatter signal 5 differs from at least two consecutive previous scatter signals 5 by at least the event threshold amount. Also, an increase of this number to 3, 4, 5, or more consecutive previous scatter signals 5 is possible. The previous scatter signals 5 can be the directly previous scatter signals 5, but they can be further in the past as well. This significantly reduces the susceptibility to noise.
In an example, the event threshold amount is fixed and identical for all frequency bins. Alternatively, though, the event threshold amount can be different for different frequency bins. This allows for setting a different sensitivity for different frequency areas. Further, the event threshold amount is user adjustable. This allows for a very flexible use of the detection sensor. The event threshold amount can be automatically dynamically adjustable. This allows for an automatic reaction to different situations.
Further, the detection sensor comprises an event threshold determiner, which is configured to determine the event threshold amount based upon an occurrence of past events, a type of detection object 3, a detection situation, a noise level, statistics of the detection signal 4, and/or statistics of the scatter signal 5. This allows for detection independent of circumstance.
The events generated by the event generator 12 are then handed on to the event interface 13, which transmits the events through the connection 15 to the event processor 20. The event processor 20 performs further processing on the events, for example, objects 3 and motion are detected based upon the events. The detailed functionality and inner workings of the event processor 20 are described in FIG. 2 .
In FIG. 2 , a detailed view of the event processor 20 of a further embodiment of the detection system 2 is shown. The event processor 20 comprises an event post-processor 22, a motion analyzer 23, and an event interpreter 24.
The event post-processor 22 performs post-processing on the events provided by the event generator 12. For example, this post-processing may comprise a statistical evaluation in the time domain and/or the frequency domain, a one-dimensional filtering regarding the frequency bins, a one-dimensional filtering regarding the observation intervals, a two-dimensional filtering regarding the frequency bins and regarding the observation intervals, and/or a plausibility check.
The motion analyzer 23 performs a motion analysis on the events provided by the event generator 12, or data generated therefrom. This can for example include data provided by the event post-processor 22. The motion analysis, for example analyzes the movement of detected objects 3, or the movement of surroundings. The event interpreter 24 interprets the events further. Especially, this interpretation can comprise a type of detected object 3, a type of movement by a detected object 3, a presence of a person, a specific person, a type of gesture performed by a person, a type of activity performed by a person, and/or a type of motion in the spatial domain or in the time domain.
It should be noted that the operation of the event post-processor 22, the motion analyzer 23, and the event interpreter 24 is of a statistical nature and data-driven. They can be implemented through model training.
In FIG. 3 , a number of signals in a further embodiment of the detection sensor 1 is shown. Here, detection signals 30 in a number of consecutive observation intervals are shown. The beginning of the respective observation intervals are denoted by t(0), t(1), and t(2). Scatter signal 31 is received in the first time interval t(0), scatter signal 32 is received in the second time interval t(1), and scatter signal 33 is received in the third time interval t(2).
On the x-axis, time is shown, while on the y-axis, the frequency, for example the individual frequency bins f(0)-f(n) are shown. The scatter signals 31-33 shown here largely follow the shape of the detection signal 30, and include only minor variations due, for example, to noise. The scatter signal 32 though comprises an area 34 with a major disturbance with regard to the transmission signal, but also with regard to the scatter signal 31, which is the previous scatter signal.
In this diagram, only the timing of the reception of the scatter signals 31-33 is shown, but not the respective amplitude. Since as described earlier, the comparison of the present scatter signal to the previous scatter signal can be performed either with regard to absolute value or with regard to phase, the timing abnormality shown in area 34, here, would register as a significant phase shift.
In FIG. 4 , further signals in a further embodiment of the detection sensor 1 are shown. On the horizontal axis, the frequency, for example the individual frequency bins f(0)-f(n) are depicted. On the vertical axis, a difference d of the previous scatter signal and the present scatter signal is shown.
Here, a difference 42 between the previous scatter signal and the present scatter signal is shown. For example, it can be a difference between the amplitude of the previous scatter signal and the present scatter signal. Alternatively, it can be a difference between the phase difference of the previous scatter signal to the detection signal and a phase difference of the present scatter signal to the detection signal. Reference number 40 a shows an upper event threshold, while reference number 40 b shows a lower event threshold. The upper event threshold 40 a is an event threshold amount compared to 0, while the lower event threshold 40 b also is the event threshold amount compared to 0.
While the difference of the previous scatter signal and the present scatter signal is between the upper event threshold 40 a and the lower event threshold 40 b, and therefore, differs from 0 by less than the event threshold amount, the event generator 12 does not generate events. The event generator 12 though generates events 45, 46, when the difference between the previous scatter signal and the present scatter signal surpasses the upper event threshold 40 a or the lower event threshold 40 b, and therefore is larger than the event threshold amount.
The event generator 12 generates a positive event 45, if the difference of the previous scatter signal and the present scatter signal is larger than the upper event threshold 40 a, and generates a negative event 46, in case the difference of the previous scatter signal and the present scatter signal is lower than the lower event threshold 40 b.
The comparison is performed frequency bin by frequency bin. This means, that the previous scatter signal within a first frequency bin is compared to the present scatter signal in the same first frequency bin. A comparison of signals between different frequency bins is not performed. Therefore, only in the frequency bins, in which the event threshold amount is exceeded by the difference of the previous scatter signal and the present scatter signal, events 45 and 46 are generated.
The events generated by the event generator 12 do not have to be differentiated in positive and negative events. Also, the generation of a single type of event no matter of the sign of the difference of the previous scatter signal and the present scatter signal is possible.
Moreover, the events 45 and 46 generated by the event generator 12 do not necessarily comprise a strength of the event. In an example, only the fact that the event threshold amount was exceeded by the difference of the previous scatter signal and the present scatter signal is recorded in the event. Alternatively, each event can also record the amount of difference of the previous scatter signal and the present scatter signal.
Finally, in FIG. 5 , an embodiment of the detection method is shown in a flow diagram. In a first step 100, a detection signal is successively generated and transmitted in a plurality of observation intervals.
In a second step 101, a scatter signal, comprising a plurality of frequency bins, resulting from a scattering of the detection signal is received in the plurality of observation intervals.
In a third step 102, a present scatter signal is compared to a previous scatter signal, separately for each of the plurality of frequency bins.
In a final fourth step 103, an event is generated for each frequency bin, in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount.
The invention is not limited to the examples and especially not to a specific number of previous scatter signals to be compared to the present scatter signal. Also, the present invention is not limited to radar sensing. Alternative active sensing technologies might be employed. For example, ultrasound sensing, terahertz sensing, or LIDAR sensing can be used. The characteristics of the embodiments can also be used in any combination. Especially, the details disclosed with regard to the device and system can also be employed with regard to the method. Every feature described in the description and/or claimed in the claims and/or shown in the drawings can be combined within this invention.

Claims

1. A detection sensor comprising:

a signal transmitter configured to successively generate and transmit a detection signal, in observation intervals,

a signal receiver, configured to receive a scatter signal, comprising a plurality of frequency bins resulting from a scattering of the detection signal in the observation intervals, and

an event generator, configured to

compare a present scatter signal to a previous scatter signal separately for each of the frequency bins, and

generate an event for each of the frequency bins in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount that corresponds to each of the frequency bins.

2. The detection sensor according to claim 1, wherein the previous scatter signal is a first previous scatter signal and the event generator is configured

to also compare the present scatter signal to a second previous scatter signal, and

to generate an event for each of the frequency bins in which the present scatter signal differs from the first previous scatter signal and the second previous scatter signal by at least the event threshold amount that corresponds to each of the frequency bins.

3. The detection sensor according to claim 1,

wherein the event threshold amount is different for at least two of the frequency bins.

4. The detection sensor according to claim 1,

wherein the present scatter signal is the scatter signal of a present observation interval, and

wherein the previous scatter signal is the scatter signal of the observation interval directly previous to the present observation interval.

5. The detection sensor according to claim 1,

wherein the event generator is configured

to compare the present scatter signal to the previous scatter signal, with regard to absolute signal values in a time domain, and/or

to compare the present scatter signal to the previous scatter signal, with regard to phase differences compared to the detection signal.

6. The detection sensor according to claim 1, further comprising:

an event interface connectable to an external event processor,

wherein the event generator is configured to transmit the event determined by the event generator for each of the frequency bins through the event interface.

7. The detection sensor according to claim 1,

wherein the signal receiver comprises a first antenna configured to receive the scatter signal, and

wherein the signal transmitter comprises a second antenna configured to transmit the detection signal.

8. A detection system comprising the detection sensor according to claim 1 and an event processor.

9. The detection system according to claim 8,

wherein the detection sensor is arranged in a first housing,

wherein the event processor is arranged in a second housing, and

wherein the first housing and the second housing are connected through a cable connection or a wireless connection.

10. (canceled)

11. The detection system according to claim 8,

wherein the event processor comprises an event post-processor configured to perform post-processing on the event generated by the event generator for each of the frequency bins, and

wherein the post-processing comprises

a statistical evaluation in a time domain and/or a frequency domain,

a one-dimensional filtering regarding the frequency bins,

a one-dimensional filtering regarding the observation intervals,

a two-dimensional filtering regarding the frequency bins and regarding the observation intervals, or

a plausibility check.

12. The detection system according to claim 8,

wherein the event processor comprises a motion analyzer configured to perform a motion analysis on the event generated by the event generator for each of the frequency bins.

13. The detection system according to claim 8,

wherein the event processor comprises an event interpreter, configured to interpret the event generated by the event generator for each of the frequency bins.

14. The detection system according to claim 13,

wherein the event interpreter is configured to determine

a type of a detected object,

a type of movement by the detected object,

a presence of a person,

a specific person,

a type of gesture performed by the person,

a type of activity performed by the person,

a type of motion in a spatial domain and/or in a time domain.

15. A method comprising:

successively generating and transmitting a detection signal, in a plurality of observation intervals,

receiving a scatter signal comprising a plurality of frequency bins resulting from a scattering of the detection signal in the observation intervals,

comparing a present scatter signal to a previous scatter signal separately for each of the frequency bins, and

generating an event for each of the frequency bins in which the present scatter signal differs from the previous scatter signal by at least an event threshold amount that corresponds to each of the frequency bins.

16. The detection sensor according to claim 1, wherein the event threshold amount is preset.

17. The detection sensor according to claim 1, wherein the event threshold amount is user-adjustable or automatically dynamically adjustable.

18. The detection sensor according to claim 1, wherein the detection sensor comprises an event threshold determiner configured to determine the event threshold amount based upon an occurrence of past events.

19. The detection sensor according to claim 1, wherein the detection sensor comprises an event threshold determiner configured to determine the event threshold amount based upon a type of detection object.

20. The detection sensor according to claim 1, wherein the detection sensor comprises an event threshold determiner configured to determine the event threshold amount based upon a detection situation.

21. The detection sensor according to claim 1, wherein the detection sensor comprises an event threshold determiner configured to determine the event threshold amount based upon a noise level.